linux-kernel - Re: [PATCH v10 27/27] KVM: x86: Don't emulate instructions guarded by CET

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Message-ID: <98fab4fd-e7a7-4b1d-aa8c-4c49c4dc7e66@intel.com>
Date: Mon, 6 May 2024 17:26:32 +0800
From: "Yang, Weijiang" <weijiang.yang@...el.com>
To: Sean Christopherson <seanjc@...gle.com>
CC: <pbonzini@...hat.com>, <dave.hansen@...el.com>, <x86@...nel.org>,
	<kvm@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<peterz@...radead.org>, <chao.gao@...el.com>, <rick.p.edgecombe@...el.com>,
	<mlevitsk@...hat.com>, <john.allen@....com>
Subject: Re: [PATCH v10 27/27] KVM: x86: Don't emulate instructions guarded by
 CET

On 5/2/2024 7:24 AM, Sean Christopherson wrote:
> On Sun, Feb 18, 2024, Yang Weijiang wrote:
>> Don't emulate the branch instructions, e.g., CALL/RET/JMP etc., when CET
>> is active in guest, return KVM_INTERNAL_ERROR_EMULATION to userspace to
>> handle it.
>>
>> KVM doesn't emulate CPU behaviors to check CET protected stuffs while
>> emulating guest instructions, instead it stops emulation on detecting
>> the instructions in process are CET protected. By doing so, it can avoid
>> generating bogus #CP in guest and preventing CET protected execution flow
>> subversion from guest side.
>>
>> Suggested-by: Chao Gao <chao.gao@...el.com>
>> Signed-off-by: Yang Weijiang <weijiang.yang@...el.com>
>> ---
> This should be ordered before CET is exposed to userspace, e.g. so that KVM's
> ABI is well defined when CET support because usable.

Sure, thanks!